In the description herein, terms “filament”, “yarn”, “tow band”, “filament denier”, “total denier”, and “packing amount” are defined as described below.
The term “filament” refers to a single fiber (monofilament) that is spun by being pushed out of one spinning hole.
The term “yarn” refers to one fiber bundle (a mass of monofilaments) that is obtained by bundling a plurality of filaments spun by one spinning cabinet together.
The term “tow band” refers to a fiber bundle of a large number of filaments, which is obtained in the following manner: bundling together all the yarns, the number of which is the same as the number of spinning cabinets, i.e., bundling all the filaments spun by a spinning machine together; and performing crimping thereon.
The term “filament denier” refers to the fineness of a filament (monofilament) in terms of a mass (g) per unit length (9000 m). In the description below, the term “filament denier” may be abbreviated as “FD”. That is, the FD of a tow band indicates the fineness of each filament forming the tow band.
The term “total denier” refers to the fineness of a tow band in terms of a mass (g) per unit length (9000 m). In the description below, the term “total denier” may be abbreviated as “TD”.
The term “packing amount” refers to the net weight of a tow band packed in one filter rod.
As one example, a tow band of cellulose acetate fibers is used as a raw material of a cigarette filter (which is also referred to as a “plug” or “filter tip”).
One example of a tow band manufacturing process is as follows. A spinning dope is prepared by dissolving cellulose acetate in an organic solvent. The spinning dope is fed into a spinning machine that includes a plurality of spinning cabinets (towers). The spinning dope is extruded through a large number of spinning holes of spinnerets that are provided for the respective spinning cabinets, and thereby a plurality of filaments are spun. The plurality of filaments are bundled together to form yarns, and then predetermined crimping is performed on the bundled yarns. As a result, a tow band is obtained. Such a tow band and a manufacturing method thereof are disclosed by Patent Literatures 1 and 2, for example.
In the manufacturing of a cigarette filter, for example, a tow band manufactured in the above-described manner is bloomed or opened; a plasticizer such as triacetin is added to the bloomed tow band, which is then formed into a cylindrical shape; rolling paper is wound around the outer periphery of the cylindrical tow band, which is then cut to a predetermined length to form a filter rod; and then the filter rod is further cut to a predetermined length, and thereby a cigarette filter is obtained.
In recent years, consumer preferences for cigarettes have been changing. Cigarettes called “super slim” or “ultra super slim”, i.e., cigarettes with a smaller diameter than that of ordinary cigarettes, have been put on the market. For example, Patent Literature 3 discloses a slim cigarette with a diameter of not less than 3.0 mm and not more than 6.0 mm, in which a tow band including filaments with a deformed cross-sectional shape such as a Y-shape is used, and a method of manufacturing a cigarette filter used for the cigarette.